BPM, Workflow, and Case

Hello, I am facing issue while reassiging the tsak to a user from coach view.

1) At first the task was with different user.

2) I assigned the task to team using task.reassignBackToRole()

3) now I am again trying to claim a task but its not happening

to claim the task I am using below code

var caseWidgetContext = window.parent.window.parent;

var workItem = new caseWidgetContext.icm.model.WorkItem(); 

workItem.repository = caseWidgetContext.ecm.model.desktop.currentRole.repository;

caseWidgetContext.pageOrchestrator.solution.retrieveCase(workItem.parentCaseId, function (parentCase) {

 workItem.caseObject = parentCase;

var wkHandler = new caseWidgetContext.icm.util.WorkItemHandler(caseWidgetContext.pageOrchestrator.page);
 wkHandler.handleWorkItem(workItem);

It doesn't give any error but its simply assign the task to previous user (the user who was there before assigning the task to team).

Thanks for your help and do not hesitate if you need more information,

Sneha